This invention relates to parenteral formulations of rapamycin 42-ester with 3-hydroxy-2-(hydroxymethyl)-2-methylpropionic acid (CCI-779).
Rapamycin is a macrocyclic triene antibiotic produced by Streptomyces hygroscopicus, which was found to have antifungal activity, particularly against Candida albcans, both in vitro and in vivo (C. Vein et al., J. Antibiot. 28, 721 (1975); S. N. Sega et al., J. Antibiot. 28, 727 (1975); H. A. Baker et al., J. Antibiot. 31, 539 (1978); U.S. Pat. No. 3,929,992; and U.S. Pat. No. 3,993,749). Additionally, rapamycin alone (U.S. Pat. No. 4,885,171) or in combination with picibanil (U.S. Pat. No. 4,401,653) has been shown to have antitumor activity.
The immunosuppressive effects of rapamycin have been disclosed. Cyclosporin A and FK-506, other macrocyclic molecules, also have been shown to be effective as immunosuppressive agents, therefore useful in preventing transplant rejection (R. Y. Calne et al., Lancet 1183 (1978); and U.S. Pat. No. 5,100,899). R. Martel et al. (Can. J. Physiol. Pharmacol. 55, 48 (1977)) disclosed that rapamycin is effective in the experimental allergic encephalomyelitis model, a model for multiple sclerosis; in the adjuvant arthritis model, a model for rheumatoid arthritis; and effectively inhibited the formation of IgE-like antibodies.
Rapamycin is also useful in preventing or treating systemic lupus erythematosus (U.S. Pat. No. 5,078,999), pulmonary inflammation (U.S. Pat. No. 5,080,899), insulin dependent diabetes mellitus (U.S. Pat. No. 5,321,009), skin disorders, such as psoriasis (U.S. Pat. No. 5,286,730), bowel disorders (U.S. Pat. No. 5,286,731), smooth muscle cell proliferation and intimal thickening following vascular injury (U.S. Pat. Nos. 5,288,711 and 5,516,781), adult T-cell leukemia/lymphoma (European Patent Application 525,960 A1), ocular inflammation (U.S. Pat. No. 5,387,589), malignant carcinomas (U.S. Pat. No. 5,206,018), cardiac inflammatory disease (U.S. Pat. No. 5,496,832), and anemia (U.S. Pat. No. 5,561,138).
Rapamycin 42-ester with 3-hydroxy-2-(hydroxymethyl)-2-methylpropionic acid (CCI-779) is ester of rapamycin which has demonstrated significant inhibitory effects on tumor growth in both in vitro and in vivo models. The preparation and use of hydroxyesters of rapamycin, including CCI-779, are disclosed in U.S. Pat. No. 5,362,718.
CCI-779 exhibits cytostatic, as opposed to cytotoxic properties, and may delay the time to progression of tumors or time to tumor recurrence. CCI-779 is considered to have a mechanism of action that is similar to that of sirolimus. CCI-779 binds to and forms a complex with the cytoplasmic protein FKBP, which inhibits an enzyme, mTOR (mammalian target of rapamycin, also known as FKBP12-rapamycin associated protein [FRAP]). Inhibition of mTOR's kinase activity inhibits a variety of signal transduction pathways, including cytokine-stimulated cell proliferation, translation of mRNAs for several key proteins that regulate the G1 phase of the cell cycle, and IL-2-induced transcription, leading to inhibition of progression of the cell cycle from G1 to S. The mechanism of action of CCI-779 that results in the G1 to S phase block is novel for an anticancer drug.
In vitro, CCI-779 has been shown to inhibit the growth of a number of histologically diverse tumor cells. Central nervous system (CNS) cancer, leukemia (T-cell), breast cancer, prostate cancer, and melanoma lines were among the most sensitive to CCI-779. The compound arrested cells in the G1 phase of the cell cycle.
In vivo studies in nude mice have demonstrated that CCI-779 has activity against human tumor xenografts of diverse histological types. Gliomas were particularly sensitive to CCI-779 and the compound was active in an orthotopic glioma model in nude mice. Growth factor (platelet-derived)-induced stimulation of a human glioblastoma cell line in vitro was markedly suppressed by CCI-779. The growth of several human pancreatic tumors in nude mice as well as one of two breast cancer lines studied in vivo also was inhibited by CCI-779.
A primary obstacle towards the formulation of CCI-779 as a parenteral dosage form is the poor aqueous solubility, which is less than 1 μg/ml. The drug is a non-electrolyte and approaches such as pH adjustment and salt formation are not useful for improving the aqueous solubility. CCI-779 has poor solubility in pharmaceutically acceptable vegetable oils but CCI-779 is soluble in certain water-miscible organic solvents that are acceptable for parenteral administration. These include ethanol, propylene glycol, polyethylene glycol and dimethylacetamide. Two problems or limitations exist with respect to the formulation of CCI-779 in these organic solvents. First, chemical instability has been noted in virtually all solvents. The instability can be due to oxidative degradation of CCI-779 or to cleavage of a lactone bond, resulting in the formation of the ring opened seco-CCI-779. Second, formulations of CCI-779 in organic solvents will precipitate upon dilution with aqueous infusion solutions, such as 0.9% Sodium Chloride Injection or 5% Dextrose Injections, or with blood. This is a primary limitation to the use of water miscible organic solvents, also referred to as cosolvents, when used as vehicles for highly water-insoluble compounds.